Oxymethylene polymers have excellent mechanical and thermal performances and, in particular, since oxymethylene copolymers have even better thermal stability and moldability than those of oxymethylene homopolymers, oxymethylene copolymers have been used as engineering plastics. Regarding methods of producing an oxymethylene copolymer, a method for producing an oxymethylene copolymer which involves bulk polymerization of trioxane and a comonomer at a temperature of 135 to 300° C. using a polymerization initiator and allows the monomer and a produced polymer to exist in a molten state during the polymerization has been publicly known (e.g., see Japanese Patent Publication No. S63-9527 (examined, approved Japanese patent application published for opposition)).
Furthermore, as a method for continuously producing oxymethylene copolymer in a homogeneous phase, a technique which involves deactivation of a polymerization initiator after polymerization is performed using a protic acid as the polymerization initiator in a cylindrical reaction vessel having a fixed stirring member, and then removal of volatile components, such as remaining monomers, from the reaction mixture by vaporization has been publicly known (e.g., see Registered Japanese Patent No. 3359748).
The Registered Japanese Patent No. 3359748 describes a production technique of an oxymethylene copolymer that can be performed using a simple and inexpensive static mixer type manufacturing facilities, without using special manufacturing facilities that are required to polymerize, pulverize, mix, melt, or transfer solid or powder, by polymerizing a monomer and a polymer in a molten state.